Agricultural implements such as harvesters generally have a crop harvesting assembly that feeds harvested crops onto a receiving assembly. In sugar beet harvesting, the crop harvesting assembly is generally configured as a line of digger wheels, the line oriented transverse to the direction of travel. Crops harvested by the line of digger wheels are typically fed onto a receiving assembly such as a grab roll assembly. The crops are then typically conveyed by a boom to a depository such as a truck or trailer bin traveling alongside the harvester.
While height control systems are known for keeping a crop harvesting assembly at a consistent height relative to the ground surface, such systems are not suitable for harvesting crops from under the ground surface and are not adequate for optimal harvesting on uneven terrain. In this description, the term “uneven” generally refers to a ground surface that is not horizontal in a direction transverse to the direction of travel, but may also include the situation where portions of the terrain are softer or harder than adjacent portions. In many instances, an uneven ground surface generally slopes in one primary direction. In the cultivation of root crops such as beets, a crop harvesting assembly typically digs into the ground at a particular depth, such as between about 2 to 4 inches under the ground surface, to pull up the crops. When digging into an uneven ground surface, one end of the line of digger wheels may dig too deeply and the other end may not dig deeply enough. On the end that digs too deeply, an excessive amount of dirt, clods and mud is pulled up by the digger wheels, thereby leading to increased clogging and downtime for cleaning and maintenance. Moreover, excess tare leads to decreased productivity. On the end that digs too shallowly, the wheels do not dig deeply enough to effectively harvest the in-ground crops.